24 research outputs found
Exploiting Network Boundaries for Spectral Clustering and Tensor Network Generative Modeling
No full textExploiting Network Boundaries for Spectral Clustering and Tensor Network Generative Modeling
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Exploiting Network Boundaries for Spectral Clustering and Tensor Network Generative Modeling
No full textIn many systems, both physical and mathematical, internal boundaries play an outsized role in dictating the large-scale behavior of the system. This theme is explored here in two parts: by identifying natural boundaries to diffusion on undirected graphs for the improvement of spectral graph methods for clustering and classification, and by imposing boundaries in two dimensional PEPS tensor networks to reduce their computational complexity for image generation. In the graph diffusion work, an algorithm is developed that identifies and removes vertices serving as bridges between well-connected clusters. With the use of this algorithm, the performance of unsupervised spectral clustering on graphs derived from synthetic point cloud data shows excellent cluster separation down to approximately two-thirds the point cloud gap size that standard spectral clustering alone tolerates. The same vertex-removal scheme applied to a diffusion-informed active learning classification algorithm shows an approximately order-of-magnitude best-case reduction in the classification error rate on benchmark hyperspectral imagery data in the low-label-query-limit versus the same active learning algorithm applied without vertex removal. The PEPS work proposes a scheme whereby such networks are cut into overlapping patch networks, whose individual contraction complexity is comparatively low. Feasibility testing is performed showing that in principle, this scheme could be used for image in-painting, and has intuitively appealing model features that are directly reflective of the data
La cosiddetta tradizione « epitomata » della Mulomedicina di Vegezio. Recensio deterior o tradizione indiretta ?
No full textSome manuscripts of the Mulomedicina of Publius Vegetius Renatus (HMNPUV) hand down a reworked and abridged text. E. Lommatzsch, the last editor of the work (Lipsiae 1903), defined this family of codices as « epitomized tradition » and put it in a secondary position in comparison with manuscripts that carry the longer text. On the contrary, a detailed inquiry (made directly on manuscripts) has pointed out that the « epitomized tradition » should be connected with the earliest stage (viii-ix century) of the tradition that we know. In this study relations have been explored among the manuscripts of this particular family and a stemma codicum has been drawn. Even if the manuscripts of the « epitomized tradition » are all rather late (XIV-XV century), linguistic and stylistic aspects indicate that its anonymous author should be placed in late antiquity or in the early Middle Ages. The aim of a reworking of Vegetius' text might be found in the attempt by the anonymous author to use the Mulomedicina for the compilation of a new veterinary treatise. Consequently, we should no longer consider the so-called « epitomized tradition » as an inferior branch of the direct tradition of the Mulomedicina, but as an autonomous work that constitutes an important source of indirect tradition. This means that in the future critical edition of Vegetius' treatise, the « epitomized » text will not overcrowd the apparatus criticus (as in Lommatzech's edition) but will be printed separate from the original (on the opposite page or in an appendix).Certains manuscrits de la Mulomedicina de Végèce (HMNPUV) transmettent un texte remanié et abrégé. Cette branche de la tradition a été définie « epitomé » par E. Lommatzsch, le dernier éditeur de la Mulomedicina (Lipsiae 1903), et classée dans une position secondaire par rapport aux manuscrits qui présentent le texte le plus long. Au contraire, une enquête détaillée, menée directement sur les manuscrits, a mis en évidence que cette recensio doit être reliée au stade le plus ancien connu de la tradition (VIIIe-IXe siècle). Dans la recherche on a exploré aussi les relations entre les manuscrits de cette famille particulière et on a tracé un stemma codicum. Bien que tous les manuscrite de cette tradition soient plutôt tardifs (XIVe-XVe siècle), des aspects linguistiques et stylistiques la font considérer comme une œuvre d'un anonyme qui peut être situé probablement dans l'Antiquité tardive ou dans le haut Moyen Age. Le but d'un remaniement du texte original de Végèce peut être recherché dans la tentative par l'auteur anonyme de réutiliser la Mulomedicina pour compiler un nouveau traité d'art vétérinaire. En conséquence, il faut conclure que la prétendue tradition en forme d'épitomè ne doit pas être considérée comme une branche deterior de la tradition directe de la Mulomedicina mais comme une œuvre à part, qui constitue une importante source de tradition indirecte. Cela entrame que dans la future édition du traité de Végèce son texte ne devra plus envahir l'appareil critique (comme dans l'édition de Lommatzsch) mais devra être publié séparément de l'original (en regard ou en appendice).Ortoleva Vincenzo. La cosiddetta tradizione « epitomata » della Mulomedicina di Vegezio. Recensio deterior o tradizione indiretta ?. In: Revue d'histoire des textes, bulletin n°24 (1994), 1994. pp. 251-274
A proposito di una recente edizione del’<em>Epitoma rei militaris di</em> Vegezio
No full textA recent critical edition of Vegetius’s Epitoma rei militaris, published by M. D. Reeve (Oxford 2004), is reviewed here. After an analysis of problems concerning the name of the author, the date of composition of the work and the drawing up of a stemma codicum, the constitution of the text of the following passages is discussed: I 10.4, I 15.2, I 19.3, I 20.3-4, I 22.1, II prol. 4-5, II 3.6, II 13.4, II 15.6, II 18.6, II 19.3, II 20.7, III 3.6, III 5.6, III 5.7, III 10.3, III 11.3, III 11.7, III 16.5, IV 1.1-2, IV 32.2, IV 38.16.Viene presa in esame la recente edizione critica dell’ Epitoma rei militaris di Vegezio curata da M. D. Reeve (Oxford 2004). Dopo la discussione delle roblematiche connesse al nome dell’autore, alla data di composizione ell’opera e alla delineazione dello stemma codicum, si tratta della costituzione del testo dei seguenti passi: I 10.4, I 15.2, I 19.3, I 20.3-4, I 22.1, II prol. 4-5, II 3.6, II 13.4, II 15.6, II 18.6, II 19.3, II 20.7, III 3.6, III 5.6, III 5.7, III 10.3, III 11.3, III 11.7, III 16.5, IV 1.1-2, IV 32.2, IV 38.16
Formation of silicon nanodots via ion beam sputtering of ultrathin gold thin film coatings on Si
No full textIon beam sputtering of ultrathin film Au coatings used as a physical catalyst for self-organization of Si nanostructures has been achieved by tuning the incident particle energy. This approach holds promise as a scalable nanomanufacturing parallel processing alternative to candidate nanolithography techniques. Structures of 11- to 14-nm Si nanodots are formed with normal incidence low-energy Ar ions of 200 eV and fluences above 2 x 10(17) cm(-2). In situ surface characterization during ion irradiation elucidates early stage ion mixing migration mechanism for nanodot self-organization. In particular, the evolution from gold film islands to the formation of ion-induced metastable gold silicide followed by pure Si nanodots formed with no need for impurity seeding
Formation of silicon nanodots via ion beam sputtering of ultrathin gold thin film coatings on Si
No full textAbstract Ion beam sputtering of ultrathin film Au coatings used as a physical catalyst for self-organization of Si nanostructures has been achieved by tuning the incident particle energy. This approach holds promise as a scalable nanomanufacturing parallel processing alternative to candidate nanolithography techniques. Structures of 11- to 14-nm Si nanodots are formed with normal incidence low-energy Ar ions of 200 eV and fluences above 2 × 1017 cm-2. In situ surface characterization during ion irradiation elucidates early stage ion mixing migration mechanism for nanodot self-organization. In particular, the evolution from gold film islands to the formation of ion-induced metastable gold silicide followed by pure Si nanodots formed with no need for impurity seeding.</p
Space, body, and mind: the application of cognitive science to the Etruscan tomb space in Tarquinia and Orvieto
No full textEtruscan painted tombs provide the earliest and most well-preserved corpus of figurative wall paintings in the ancient Mediterranean. Depictions of musicians, banqueters, and other images provide a vibrant array of social and performative events inside a small subset of chambered tombs in central Italy. In part, the rarity of tomb paintings in Etruria, along with their figurative nature, have contributed to a surplus of scholarship related to the tomb paintings themselves. Such perspectives tend to emphasise the presumed meaning of visual imagery inside the tomb, rather than how the tomb space was cognitively and somatically experienced during the interment. Consequently, crucial areas of the tomb, such as the dromos, have been minimised, and burial rites originally performed inside the painted tomb remain unclear. I argue that further clarifying sensory mechanisms underlying sight, sound, and space offers a novel way forward in confronting this reality.
This thesis seeks to re-contextualize the Etruscan painted tomb with respect to the physical and cognitive experience of funerary ritual. Rather than singly assessing bodily movement or tomb paintings, the tomb is considered from an emic perspective, as a bounded space with unique visual, spatial, and acoustic properties. Fieldwork data involving sound propagation from 14 painted tombs in Tarquinia and Orvieto are presented along with intact photogrammetric and acoustic models illustrating the painted tomb as an intact navigable space. Such interpretation, when applied in conjunction with existing scholarship, provides a clearer understanding of the Etruscan painted tomb space whilst generating new avenues of research in pre-Roman archaeology. Perhaps most importantly, the Etruscan record is allowed to assume precedence over the words and materiality of another culture, language, author, or object
The significance of in situ conditions in the characterization of GaSb nanopatterned surfaces via ion beam sputtering
No full textA systematic study is conducted in order to elucidate the underlying mechanism(s) for nanopatterning with low-energy irradiation of GaSb (100) under normal incidence. Ion energies between 50 and 1000 eV of Ar+ and ion fluences of up to 10(18) cm(-2) were employed. Characterization of the shallow (e.g., 1 to 6 nm) amorphous phase region induced by irradiation and the subsurface crystalline phase region is accomplished with low-energy ion scattering spectroscopy and x-ray photoelectron spectroscopy, respectively. In situ studies are conducted due to the strong chemical affinity for oxygen of GaSb. The studies conclude that at energies below 200 eV, the native oxide layer hampers nanopatterning until it becomes removed at a fluence of approximately 5 x 10(16) cm(-2). At this energy and threshold fluence, the surface is enriched with Ga atoms during irradiation. At energies above 200 eV, the native oxide layer is efficiently removed in the early irradiation stages, and thus the detrimental effects from the oxide on nanopatterning are negligible. In situ surface concentration quantification indicates that the surface enrichment with Sb atoms in the amorphous phase layer increases with the incident ion energy. Post-air exposure characterization reveals that the measured enrichment of the surface with gallium is due to oxygen reduction by Ga atoms segregated from both the amorphous and the crystalline phase regions as a result of air exposure. (C) 2011 American Institute of Physics. [doi:10.1063/1.3642997
Study of scalable IBS nanopatterning mechanisms for III-V semiconductors using in-situ surface characterization
No full textABSTRACTIon-beam sputtering (IBS) has been studied as a means for scalable, mask-less nanopatterning of surfaces. Patterning at the nanoscale has been achieved for numerous types of materials including: semiconductors, metals and insulators. Although much work has been focused on tailoring nanopatterning by systematic ion-beam parameter manipulation, limited work has addressed elucidating on the underlying mechanisms for self-organization of multi-component surfaces. In particular there has been little attention to correlate the surface chemistry variation during ion irradiation with the evolution of surface morphology and nanoscale self-organization. Moreover the role of surface impurities on patterning is not well known and characterization during the time-scale of modification remains challenging. This work summarizes an in-situ approach to characterize the evolution of surface chemistry during irradiation and its correlation to surface nanopatterning for a variety of multi-components surfaces. The work highlights the importance and role of surface impurities in nanopatterning of a surface during low-energy ion irradiation. In particular, it shows the importance of irradiation-driven mechanisms in GaSb(100) nanopatterning by low-energy ions and how the study of these systems can be impacted by oxide formation.</jats:p
